Thermoelectric cryoprobe

ABSTRACT

A thermoelectric cryoprobe comprising a handle composed of two electrically insulated halves made of a material possessing high heat conduction. One end of the handle is tapered, and a semiconductor cooling thermoelement is arranged at the butt of the tapered end. The height of the thermoelement does not exceed the radius thereof. The surface of a commutation plate of the thermoelement is the working surface of the thermoelectric cryoprobe.

FIELD OF THE INVENTION

This invention relates to thermoelectric refrigerating plants and, inparticular, to thermoelectric cryoprobes.

BACKGROUND ART

In modern practice the most popular medical cryoprobes make use ofgaseous or liquid refrigerants (carbon dioxide, freons, liquid nitrogenand others) which can be divided into two basic types, according to themethod of refrigerant supply, namely cryoprobes with discrete andcontinuous types of supply.

Cryoprobes of the first type are basically reservoirs filled with liquidrefrigerants in advance to cool a metal rod. The latter is in fact theprobe. The temperature of the cryoprobe tip cannot, therefore, becontrolled in any way in the course of an operation and is relativelylow (about -40° C.).

The probe can be warmed up in case of a dangerous development in theoperation (deep freezing, freezing of surrounding tissue, etc.) by meansof a warm sterile liquid fed directly to the freezing area.

The process of warming up is lengthy (tens of seconds) and reapplicationof the cryoprobe in the operation required refilling of the refrigerant.

The above mentioned unfavourable developments are even more frequentsince the cryoprobe is introduced into the operation field alreadycooled, as well as due to the fact that the probe tip has cooled sidesurfaces.

Cryoprobes using continuously supplied refrigerant are much moreefficient, but, consequently, more complicated. In this case use is madeof complex gas apparatuses, maintenance becomes quite a problem, as wellas preparation of the cryoprobe for an operation. A great reserve ofrefrigerant is a necessity.

A new medically oriented cryoprobe based on the Peltier effect method ofthermoelectric cooling was proposed in the 60's (cf., for example, I. K.Poltinnikova, E. A. Kolenko, Intracapsular Extraction of a Cataract bySemiconductor Device. Ophthalmotological Magazine, No. 8, 1964,pp.563-566. in Russian).

The medical thermoelectric cryoprobe comprises a semiconductor coolingthermoelement and a double handle. The p and n branches of thethermoelement are mounted on the two halves of the handle.

Refrigerating power of the thermoelement is concentrated on thefunctional surface of the cryoprobe which is in fact a metalconcentrator-tip placed on the switching plate of the thermoelement. Thespecific refrigeration effect of the functional cryoprobe surfacerequired for freezing is attained in this manner.

Heat sink from the hot junctions of such thermoelements in cryoprobes iseffected with the help of running water circulating inside the handle.The masive concentrator-tip determines in this case great thermalinertia of the cryoprobe. For cooling such a cryoprobe should be cut in3 minutes before freezing the tissue. It is, therefore, still necessaryto introduce a pre-cooled probe into the operation field, its sidecooled surfaces being large as compared to the functional workingsurface.

As it has already been mentioned these features are liable to producedangerous developments in operations, particularly in ophthalmologicaloperations where the field of operation is very small.

Moreover, in such conditions water cooling hoses feeding water to thecryoprobe handle make it very hard to manipulate the cryoprobe.

DISCLOSURE OF THE INVENTION

The invention resides in providing a miniature, quick responsethermoelectric cryoprobe which is electronically cooled by means of anew thermal circuit.

This object is achieved in that in a thermoelectrical cryoprobecomprising a semiconductor cooling element and a handle made up of twoelectrically separated parts, according to the invention, one end of thehandle is narrowed and the butt end thereof carries a semiconductorcooling thermoelement whose height does not exceed the radius thereof,the surface of the switching plate of said thermoelement being theworking surface of the cryoprobe, the two parts of the handle being madeof a material possessing high heat conduction.

The proposed thermoelectric cryoprobe offers the following usefulfeatures.

Low thermal inertia. The minimum temperature of the working surface isattained in 1-8 seconds after the cryoprobe is switched on. Thecryoprobe can be introduced into the operation field while still warmand attain the working temperature practically instantly after beingapplied to a spot most suitable for freezing.

Cooling is localized on the working surface of the cryoprobe, there areno side surfaces which can freeze up the surrounding tissue.

The cryoprobe can be defreezed from the tissue in 1 or 2 secondscounting from the moment the probe is switched out. The cryoprobe isthen ready for a repeated cryaction cycle.

The cryoprobe is connected to external devices by means of a thinelectric cable which in no way hinders the surgeon's movements.

These advantages sharply decrease probability of unfavourabledevelopments during an operation and permit modern methods of multipleapplications of the cryoprobe.

Extreme ease of maintenaince and preparation for operations of thecryoprobe is another important advantage of the proposed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference toa specific embodiment thereof, taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 illustrates a general view of a thermoelectric cryoprobe,according to the invention;

FIG. 2 illustrates an enlarged view of a part of a handle of athermoelectric cryoprobe equipped with a thermoelement;

FIG. 3 illustrates a view taken along line III--III of FIG. 1, accordingto the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The proposed thermoelectric cryoprobe comprises, in accordance with theinvention, a semiconductor thermoelement 1 (FIG. 1) mounted on a butt ofa narrowing end of a handle 2.

The handle 2 has two halves 3 and 4 (FIG. 2) which are metalhalf-cylinders secured together with a dielectric gasket 5 insetedtherebetween. The butt end of the handle 2 opposite to the semiconductorthermoelement 1 (FIG. 1) has an electric connector 6 coupling the parts3 and 4 of the handle to the current carrying wires of a two-coreelectric cable 7. The parts 3 and 4 of the handle 2, according to theinvention, are made of a material possessing high heat conduction, ofcopper, for example.

The semiconductor thermoelement 1 comprises two semiwashers 8 and 9(FIG. 2) made of known thermoelectric materials based on bismuth andantimony tellurides.

The semi-washers 8 and 9 are connected by a silver commutation plate 10whose thickness does not exceed 0.1 mm. The commutation plate 10 formsthe cold junction of the semiconductor thermoelement 1 and itsfunctional surface is the working surface of the cryoprobe.

Hot butt ends of the semi-washers 8 and 9 of the thermoelement 1 aresoldered directly on the butt ends of the parts 3 and 4 of the handle 2and are in good electrical and thermal contact therewith, thus forminghot junctions of the semiconductor thermoelement 1.

The surfaces of the handle 2 are chrome plated in order to protect themfrom the sterilizing solutions. The side surfaces of the semiconductorthermoelement 1 are coated by an epoxy resin film.

A medical thermoelectric cryoprobe for cryoextraction of a lens has asemiconductor thermoelement whose diameter does not exceed 2 mm. Theheight of the semiconductor thermoelement 1 in this case is not morethan 1 mm.

The thermoelectric cryoprobe operates as follows. Electric current isfed from a rectifier or some other DC power source (not shown) via thecable 7 (FIG. 1) and the connector 6, to the parts 3 and 4 (FIG. 2) ofthe handle 2, the semi-washers 8 and 9 and the commutation plate 10 ofthe semiconductor thermoelement 1. The commutation plate 10 is thereforecooled. The voltage supplied to the parts 3 and 4 of the handle 2 isabout 0.1 volts, current intensity is about 10 a.

It is common knowledge that the specific refrigerating power of thesemiconductor thermoelement 1 (the refrigerating effect of a unit ofarea of the cold junction) grows with the decrease of the heightthereof. With the height of the semiconductor thermoelement 1 limited inaccordance with the invention, the commutation plate 10 alone, without aconcentrator tip, sufficient for freezing up the lens of the eye.

Thus the commutation plate 10 becomes the working organ of the cryoprobeand the thermal lag of the thermoelectric cryoprobe depends upon thethermal inertia of the thermoelement 1 alone. In other words, the timerequired for the thermoelectric cryoprobe to attain its workingtemperature coincides with the time required for the semiconductorthermoelement 1 to attain its stationary working temperature.

This temperature is in inverse proportion to the height of thesemiconductor thermoelement. With the height of the semiconductorthermoelement 1 limited in accordance with the invention, the stationaryworking temperature thereof is reached in one to two seconds aftercurrent is turned on thus ensuring a short thermal lag of the cryoprobe.

Heat liberated by hot junctions of the semiconductor thermoelement 1flows via the tapered portion of the handle 2 and is further partiallyaccumulated by this handle 2 and partially dissipated.

Reliable heat removal from the hot junction is also facilitated by thematerial of the parts 3 and 4 of the handle 2, possessing high thermalconduction, copper, in particular, which is one of the forerunners amongmetals as far as heat conduction is concerned.

Some heat liberated by the semiconductor thermoelement 1 is accumulatedby the handle 2 in quasistationary conditions where the temperature ofthe hot junction varies. But such variations prove insignificant andlead to no substantial change in the temperature of the commutationplate 10, which is in contact with the cooled tissue, even duringperiods many times over the time required for lens extraction.

The thermoelectric cryoprobe is warmed up and defreezed from tissue whencurrent is cut off. Heat flows to the freezed-up tissue from the handle2 via the thermoelement 1 whose height is limited so intensively thatthe tissue is released in 1 or 2 seconds after current is cut off.

Numerous clinical experiments with the thermoelectric cryoprobe havedemonstrated that it is very effective in cataract removal operations,in some brain operations and other instances where medium-temperature(not more than -20° C.) local cooling of tissues is required forreliable surface freeze-up.

INDUSTRIAL APPLICABILITY

The invention can used in manufacturing miniature cryoprobes in medicineand, in particular, for ophthalmological operations.

We claim:
 1. A thermoelectric cryoprobe, comprising:a handle comprising two electrically separated longitudinal half-cylinders made of a high heat conduction material; a semiconductor cooling thermoelement having a hot junction in contact with said two half-cylinders, said thermoelement including a commutation plate mounted on one end of said handle and in direct contact with the latter by said hot junction, the height of said thermoelement does not exceed its radius, and said commutation plate having a functional surface which is a working surface of said thermoelectric cryoprobe; a heat sink for removal of heat from said semiconductor cooling thermoelement, said heat sink comprising said two electrically separated longitudinal half-cylinders forming part of said handle; and means for feeding current to the longitudinal half-cylinders of said handle.
 2. The probe of claim 1, wherein one of the ends of said handle is tapered.
 3. The probe of claim 2, wherein said semiconductor cooling thermoelement is mounted on said tapered end.
 4. The probe of claim 3, wherein said commutation plate has a thickness not exceeding 0.1 mm and forms the cold junction of said semiconductor thermoelement.
 5. The probe of claim 1, including a dielectric gasket between said two half-cylinders.
 6. The probe of claim 1, wherein said current feeding means includes an electrical connector connecting said two half-cylinders to a two core electrical cable.
 7. The probe of claim 1, wherein said semiconductor thermoelement comprises two semi-washers connected to and by said commutation plate.
 8. The probe of claim 7, wherein said commutation plate has a thickness not exceeding 0.1 mm.
 9. The probe of claim 7, wherein said two electrically separated half-cylinders each have a butt end, and said semi-washers are soldered directly onto said butt ends to form hot junctions of said semiconductor thermoelement.
 10. The probe of claim 9, wherein the surface of said handle is chrome-plated.
 11. The probe of claim 1, wherein said thermoelement has a diameter not exceeding 2 mm.
 12. The probe of claim 1, wherein the height of said thermoelement does not exceed 1 mm.
 13. The probe of claim 1, wherein said commutation plate has a thickness not exceeding 0.1 mm.
 14. A thermoelectric cryoprobe, comprising:a handle including two electrically separated longitudinal metal half-cylinders each made of a high heat conduction material; one end of said handle being tapered; a semiconductor cooling thermoelement having a hot junction and including a commutation plate mounted on said tapered end of said handle and in direct contact therewith by said hot junction, the height of said thermoelement does not exceed its radius, said hot junction being in contact with said two half-cylinders, and said commutation plate having a functional surface which is a working surface of said thermoelectric cryoprobe; a heat sink for removal of heat from said semiconductor cooling thermoelement, said heat sink including and being formed from said two electrically separated half-cylinders forming part of said handle; and means for feeding current to the longitudinal half-cylinders of said handle.
 15. The probe of claim 14, including a dielectric gasket between said two metal half-cylinders.
 16. The probe of claim 15, wherein said current feeding means includes an electrical connector connecting said two metal half-cylinders to a two core electrical cable.
 17. The probe of claim 16, wherein said semiconductor thermoelement comprises two semi-washers connected to and by said commutation plate.
 18. The probe of claim 17, wherein said semi-washers are soldered directly onto butt ends of said two electrically separated half-cylinders to form hot junctions of said semi-conductor thermoelement.
 19. The probe of claim 18, wherein said commutation plate has a thickness not exceeding 0.1 mm and forms the cold junction of said semiconductor thermoelement.
 20. The probe of claim 19, wherein said thermoelement has a diameter not exceeding 2 mm and a height not exceeding 1 mm. 